Once the engine has warmed up and accelerating it backfires and shakes

1991 CHEVROLET 2500
350,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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DGRIFFITH528
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The engine runs good until it warms up. Then when you accelerate the engine will shake and backfire until you let the Throttle go back to an ideal speed.
When this started it was backfiring, so I took the plugs out and checked the compression. I found that one cylinder had a bent pushrod. I didn’t check any of the other pushrods The oil pressure is at 30 when the motor is hot.
The engine has been good cold, but it will not run good.
May 17, 2022 at 9:16 AM
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KASEKENNY
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Just to be sure, you did not repair the bent push rod. If that is the case, then we need to do that because that can cause issues like this. However, it sounds like since it runs well until it is warm, that this is not causing this specific issue.

https://www.2carpros.com/articles/engine-backfires-while-running

https://youtu.be/HiI_eeFg-2A

I would suggest we start with two things. First let's start to check the fuel pressure when the engine starts and then as it warms up just to see what this is doing.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

The other things that we need to check is to monitor the o2 sensor data when this starts running poorly. Clearly, we should be able to start seeing the o2 data change when this starts to run poorly.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Basically, I think we have an o2 sensor issue, but we need to see what these are saying and get this other info and go from there.

Thanks
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May 18, 2022 at 9:41 AM